Intelligently hash asset files

data/layout.jade

@@ -57,7 +57,7 @@ doctype html
 html
   head
     meta(charset='utf-8')
-    link(rel='stylesheet' href=(base + 'assets/style.css?t=' + (+new Date())))
+    link(rel='stylesheet' href=(base + 'assets/style.css?t=' + hash.style))
     title= title
   body.-menu-visible
     .doc-layout
@@ -67,4 +67,4 @@ html
           != contents
       .menu.toc-menu
         +menu(toc, 0)
-    script(src=(base + 'assets/script.js?t=' + (+new Date())))
+    script(src=(base + 'assets/script.js?t=' + hash.script))

index.js

@@ -8,6 +8,7 @@ const assign = Object.assign
 
 const buildJs = require('./lib/build_js')
 const buildCss = require('./lib/build_css')
+const hash = require('./lib/hash')
 
 /**
  * Metalsmith middleware
@@ -78,9 +79,14 @@ function relayout (files, ms, done) {
     const file = files[fname]
     const base = Array(fname.split('/').length).join('../')
     file.contents = layout(assign({}, file, {
-      base, toc, index, active: fname
+      base, toc, index, active: fname,
+      hash: {
+        style: hash(files['assets/style.css'].contents),
+        script: hash(files['assets/script.js'].contents)
+      }
     }))
   })
 
   done()
 }
+

lib/hash.js

@@ -0,0 +1,7 @@
+const crypto = require('crypto')
+
+module.exports = function hash (data) {
+  const shasum = crypto.createHash('sha1')
+  shasum.update(data)
+  return shasum.digest('hex').substr(0, 8)
+}

test/fixture_test.js

@@ -31,9 +31,15 @@ describe('fixture', function () {
     it('highlights current menu item', function () {
       expect(data).toMatch(/-active[^>]+>onmount/)
     })
+
     it('adds "link-slug" classes', function () {
       expect(data).toMatch(/link-index[^>]+>onmount/)
     })
+
+    it('adds hash to assets', function () {
+      expect(data).toMatch(/script\.js\?t=[a-f0-9]{8}/)
+      expect(data).toMatch(/style\.css\?t=[a-f0-9]{8}/)
+    })
   })
 
   describe('style.css', function () {